Water classification method for estuary nutrient criteria based on ecological response difference

Abstract

This embodiment discloses a method for classifying and zoning estuarine nutrient benchmark water bodies based on ecological response differences, relating to the field of environmental protection and comprehensive resource utilization technology. By using the multi-year average salinity of the surface layer of the target area for water body classification and zoning, the topography of the target area, and the tidal river interface of the target area, the river-estuary boundary, the estuary side boundaries, and the estuary-nearshore boundary within the target area are determined, thus defining the estuarine region within the target area. Then, estuarine unit zoning indicators are used to determine the boundaries of estuarine zoning units within the estuarine region. By using the probability value of a significance test within the estuarine zoning units, if the selected estuarine unit zoning indicators are determined to be ecologically relevant, the final estuarine zoning units within the estuarine region are determined, completing the water body classification and zoning of the target area. The zoning elements and division standards of this invention conform to the nutrient benchmarks characteristic of my country's marine ecological environment.

Description

Technical Field

[0001] This invention relates to the field of environmental protection and comprehensive resource utilization technology, and in particular to a method for classifying and zoning estuarine nutrient baseline water bodies based on differences in ecological response. Background Technology

[0002] Estuarine nutrient water quality benchmarks represent the maximum concentrations or levels that do not have harmful impacts on the marine ecosystem (such as anthropogenic eutrophication of estuarine waters, eutrophication-driven red tides, and hypoxia), and serve as the scientific basis for estuarine nutrient pollution management and control. Determining nutrient benchmarks that conform to the characteristics of my country's marine ecological environment is helpful in improving the comprehensive ecological and environmental management level of key marine areas in my country and is of significant strategic importance for achieving sustainable marine development. Because the concentrations of different forms of nutrients fluctuate significantly across different climatic zones, hydrodynamic conditions, input methods, and seasons, and because estuaries and adjacent sea areas generally possess distinct characteristics, it is generally impossible to recommend a national-level nutrient water quality benchmark applicable to all sea areas. It is necessary to develop regionally specific estuarine nutrient water quality benchmarks based on the characteristics and water types of different nearshore sea areas.

[0003] Water body classification and zoning are the prerequisite and foundation for establishing estuarine nutrient water quality benchmarks. Physical classification groups similar estuaries, tributaries, or coastal waters into the same area, reducing the scale of benchmark-setting issues and improving management responsiveness. Within the same water body zone, due to similar hydrological and water quality conditions, aquatic biological characteristics, and response characteristics to nutrient inputs, water productivity and nutrient status exhibit a good correlation, providing a solid foundation for establishing nutrient water quality benchmarks. Simultaneously, the variability of ecosystem-related monitoring indicators (such as water quality factors) should be reduced within different zones to maximize inter-zone diversity.

[0004] Since the 1980s, countries and international organizations such as the United States and the European Union have gradually established their own water body classification and zoning methods and indicator systems, taking into full account the differences in natural regions and ecosystems. In 2001, the United States published the "Technical Guidelines for the Establishment of Nutrient Benchmarks in Estuaries and Coastal Areas," proposing water body zoning principles covering multiple key factors such as topography, hydrodynamic factors, and habitat communities. However, given the complexity of the relevant requirements, various states often did not fully follow these guidelines in their water body zoning practices. In 2003, the European Union proposed a typological-based method for estuarine water body zoning. This method uses simple physical classification to divide water body zoning units that are both ecologically relevant and easy to implement. However, its zoning elements and standards are not well-suited to the estuarine ecosystems in my country and cannot be directly applied. Domestic research on estuarine water body zoning started relatively late and is limited. Related research mainly focuses on specific estuaries such as the Yangtze River Estuary and the Jiulong River Estuary, conducting water body classification and zoning studies based on natural geographical characteristics. Summary of the Invention

[0005] This invention discloses a method for classifying and zoning estuarine nutrient baseline water bodies based on differences in ecological response, in order to overcome the above-mentioned technical problems.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A method for classifying and zoning estuarine nutrient baseline water bodies based on differences in ecological response includes the following steps: S1: Obtain the multi-year average salinity of the surface layer of the target area for water body classification and zoning, the topography of the target area, and the tidal river interface of the target area. S2: Based on the multi-year average salinity of the surface water in the target area, the topography of the target area, and the tidal river section interface of the target area, the Venice salinity classification system is used to determine the river-estuary boundary, the two sides of the estuary boundary, and the estuary-nearshore boundary in the target area to be classified and zoned, so as to determine the estuary area in the target area. S3: Select any estuary unit zoning index to determine the boundary of the estuary zoning unit within the estuary area, so as to obtain several estuary zoning units within the estuary area. S4: Obtain the test statistics within the estuary zoning unit to determine the probability value of the significance test within the estuary zoning unit, and then determine whether the selected estuary unit zoning indicators have ecological relevance. If the selected estuary unit zoning indicators are not ecologically relevant, then S3 is executed again based on the reselected estuary unit zoning indicators; until the selected estuary unit zoning indicators are ecologically relevant; the final estuary zoning units within the estuary area are determined, and the water body classification and zoning of the target area is completed.

[0007] Furthermore, the method used to determine the river-estuary boundaries within the target area for water body classification and zoning is as follows: S21: Obtain the multi-year average salinity of the surface layer of the water body within the target area to be classified and zoned, so as to obtain the multi-year average isosalinity line within the target area; and then determine the salinity-based river-estuary boundary of the target area based on the multi-year average isosalinity line. S22: Determine the topographic-based river-estuary boundary of the target area; S23: Determine the river-estuary boundary of the target area based on the tidal section interface; S24: Based on the river-estuary boundary based on salinity, the river-estuary boundary based on topography, and the river-estuary boundary based on the tidal section interface, obtain the degree of spatial overlap between any two river-estuary boundaries, so as to determine the overlapping area of ​​the buffer zone of the two river-estuary boundaries with the highest degree of overlap, and then determine the final river-estuary boundary of the target area.

[0008] Furthermore, the formula used to obtain the degree of spatial overlap between any two river-estuary boundaries is as follows: (1) In the formula: The first The river-estuary boundary and the first The buffer zone area of ​​the river-estuary boundary; For the first The buffer zone of the river-estuary boundary and the first The area of ​​the overlapping buffer zone of the river-estuary boundary; For the first The river-estuary boundary and the first The degree of spatial overlap between the river-estuary boundaries; All are indexes of river-estuary boundaries.

[0009] Furthermore, the method for obtaining the test statistic within the estuarine zoning unit is as follows: When the number of estuarine zoning units is 2, an improved Mann-Whitney statistic calculation method is used to obtain the Mann-Whitney statistic for the estuarine zoning units in terms of biological and ecological indicators. The formula used is as follows: (2) (3) (4) In the formula, For the first The estuary partition unit is relative to the first Mann-Whitney statistics for each estuarine zoning unit on the k-th type of biological ecological indicator; For the first The estuary partition unit is relative to the first Mann-Whitney statistics for each estuarine zoning unit on the k-th type of biological ecological indicator; For the first The number of sampling points in each estuary zoning unit; For the first The number of sampling points in each estuary zoning unit; For the first The rank sum of the ratio of the number of the k-th type of biological and ecological indicators to the sum of the number of all biological and ecological indicators at all sampling points in a river estuary sub-unit after mixed sorting; For the first The rank sum of the ratio of the number of the k-th type of biological and ecological indicators to the sum of the number of all biological and ecological indicators at all sampling points in a river estuary sub-unit after mixed sorting; An index for biological and ecological indicators; This is the statistic used for significance testing; and All are index numbers of the estuary subdivision units; When the number of estuarine zoning units is greater than 2, an improved Kruskal-Wallis statistic calculation method is used to obtain the Kruskal-Wallis test statistics of the estuarine zoning units on biological and ecological indicators. The formula used is as follows: (5) (6) In the formula: The total number of sampling points for the k-th type of biological ecological indicator within the estuary area; This represents the total number of estuarine subdivision units; For the first The number of sampling points in each estuary zoning unit; For the first The rank sum of the ratio of the number of the k-th type of biological and ecological indicators to the sum of the number of all biological and ecological indicators at all sampling points in a river estuary sub-unit after mixed sorting; This is the Kruskal-Wallis test statistic for the k-th type of biological ecological indicator.

[0010] Furthermore, the biological and ecological indicators include: nutrient use efficiency, phytoplankton cell density, number of phytoplankton species, proportion of phytoplankton group cell density to the total phytoplankton cell density, phytoplankton diversity index, phytoplankton richness index, and phytoplankton evenness index. Among them, nutrient salt utilization efficiency includes: chlorophyll a / total nitrogen, chlorophyll a / dissolved inorganic nitrogen, chlorophyll a / total phosphorus, and chlorophyll a / reactive phosphate. Phytoplankton include diatoms, dinoflagellates, cyanobacteria, green algae, golden algae, and yellow algae.

[0011] Furthermore, after S4, the method further includes: selecting estuarine zoning unit evaluation indicators to evaluate the estuarine zoning unit; wherein the selected estuarine zoning unit evaluation indicators include biological and ecological indicators, water quality status indicators, and hydrological habitat indicators. The water quality indicators include total nitrogen, dissolved inorganic nitrogen, nitrate nitrogen, nitrite nitrogen, ammonia nitrogen, total phosphorus, reactive phosphate, dissolved oxygen at the bottom, transparency, and suspended solids; The hydrological habitat indicators include salinity, water depth, water temperature, stratified mixing characteristics, tidal range, salinity front, distribution of the maximum turbidity zone, sediment type, and water residence time.

[0012] Beneficial Effects: This invention provides a method for classifying and zoning estuarine nutrient benchmark water bodies based on ecological response differences. By analyzing the multi-year average salinity of the surface layer of the target area, the topography of the target area, and the tidal river interface, the river-estuary boundary, the estuary side boundaries, and the estuary-nearshore boundary within the target area are determined, thus defining the estuarine region within the target area. Then, estuarine unit zoning indicators are used to determine the boundaries of estuarine zoning units within the estuarine region. Finally, by using the probability values ​​of significance tests within the estuarine zoning units, and confirming the ecological relevance of the selected estuarine unit zoning indicators, the final estuarine zoning units within the estuarine region are determined, completing the water body classification and zoning of the target area. The estuarine zoning units obtained by this invention have high adaptability to the estuarine ecosystems of my country and conform to the nutrient benchmarks characteristic of my country's marine ecological environment. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a flowchart of the method for classifying and zoning estuarine nutrient baseline water bodies based on differences in ecological response, as presented in this invention. Figure 2 This is a schematic diagram of a river estuary with a branching structure in an embodiment of the present invention; Figure 3 This is a schematic diagram of a river estuary without a branching structure in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the proportion of phytoplankton groups at different salinities in an embodiment of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] This embodiment introduces a method for classifying and zoning estuarine nutrient baseline water bodies based on ecological response differences, including the following steps: Figure 1 As shown: S1: Obtain the multi-year average salinity of the surface layer of the target area for water body classification and zoning, the topography of the target area, and the tidal river interface of the target area. In this embodiment, the geographic hydrological data of the target area includes geographic information such as the latitude and longitude range of the target area, the sea area located in my country, and the administrative regions covered. Specifically, the geographic hydrological data acquisition includes determining the latitude and longitude range of the target area, the sea area located in my country, and the administrative regions covered; acquiring the names, number, and watersheds of rivers flowing into the sea within the target area, and collecting information on the distribution of tidal river interfaces of major rivers flowing into the sea; calculating the average runoff of major rivers flowing into the sea over the past 5 years, 10 years, and many years, and analyzing the interannual variation pattern of runoff; and acquiring data such as salinity, water depth, water temperature, tidal range, salinity front and maximum turbidity zone distribution, water residence time, and sediment types within the target area.

[0017] In this embodiment, the method for obtaining the multi-year average salinity of the surface water layer in the target area is as follows: If nationally monitored salinity data exists in the target area for water body classification and zoning, then the nationally monitored salinity data shall be used as the salinity in the target area for water body classification and zoning. When there is no nationally monitored salinity data in the target area for water body classification and zoning, local monitored salinity data shall be used as the salinity in the target area for water body classification and zoning. If local salinity monitoring data is unavailable, salinity data predicted by a predictive model will be used as the salinity within the target area for water body classification and zoning.

[0018] Specifically, the water quality data in this embodiment includes data on total nitrogen, dissolved inorganic nitrogen, nitrate nitrogen, nitrite nitrogen, ammonia nitrogen, total phosphorus, reactive phosphate, dissolved oxygen at the bottom layer, transparency, and suspended solids in rivers, estuaries, and nearshore areas.

[0019] Specifically, the biological and ecological data in this embodiment include data such as chlorophyll a, phytoplankton species, and cell density in rivers, estuaries, and nearshore areas; by analyzing the species composition, dominant species, dominant groups, and diversity index of phytoplankton, macroalgae, seagrass, and other organisms in the region, the location and extent of special ecological areas such as marine protected areas and ecological monitoring areas distributed in the region are clarified.

[0020] Specifically, this embodiment collects data on the frequency of occurrence, scope of impact, interannual variation, and seasonal variation patterns of ecological and environmental problems such as red tides, hypoxia, and eutrophication caused by excessive nitrogen and phosphorus input in the target area.

[0021] S2: Based on the multi-year average salinity of the surface water in the target area, the topography of the target area, and the tidal river section interface of the target area, the Venice salinity classification system is used to determine the river-estuary boundary, the two sides of the estuary boundary, and the estuary-nearshore boundary in the target area to be classified and zoned, so as to determine the estuary area in the target area. Preferably, the method used to determine the river-estuary boundary within the target area for water body classification and zoning is as follows: S21: Obtain the multi-year average salinity of the surface layer of the water body within the target area to be classified and zoned, so as to obtain the multi-year average isosalinity line within the target area; and then determine the salinity-based river-estuary boundary of the target area based on the multi-year average isosalinity line. This embodiment implements quality control on the data sources for acquired salinity: when national-level salinity monitoring data exists, it is used; when national-level salinity monitoring data does not exist, if local-level or literature-reported salinity monitoring data exists, it is used; otherwise, existing salinity prediction models are used to obtain predicted salinity data. In other words, national-level monitoring data is prioritized, followed by local-level or literature-reported monitoring or detection data, and finally, model-predicted data. The station locations for salinity data are highly representative and can objectively reflect the salinity distribution characteristics and variation patterns in the estuary area.

[0022] Specifically, this embodiment uses the multi-year average surface salinity of the target area for water body classification and zoning: In terms of spatial dimension (sampling level), since the massive proliferation of phytoplankton caused by eutrophication usually occurs in the sea surface, using surface salinity can better reflect the differences in the sensitivity of ecosystems in different regions to nutrient responses. In terms of temporal dimension (year selection), multi-year average salinity can reduce the interference of anomalous data under extreme / occasional climate conditions. The years used for salinity are determined based on the variation characteristics of the annual runoff of the main rivers flowing into the sea in the region, with priority given to continuous year sequences (usually 5 to 10 years) where the runoff is basically the same as the multi-year average.

[0023] Specifically, after obtaining the multi-year average salinity of the water surface, the multi-year average isosalinity lines of the target area are drawn using the spatial analysis tools in ArcGIS software, including interpolation analysis (inverse distance weighting method, kriging method) and raster surface contour lines in the 3D analysis tools.

[0024] In this embodiment, the salinity boundary value is determined with reference to the international mainstream Venetian salinity classification system, and the river-estuary boundary is determined based on the isohaline with salinity of a.

[0025] S22: Determine the topographic-based river-estuary boundary of the target area; Specifically, for estuaries with clearly defined bifurcation structures, the boundary is demarcated based on the bifurcation apex, combined with the natural extension lines of the shorelines on both banks, to establish a complete topographic-based river-estuary boundary. For estuaries without obvious bifurcations, the boundary is determined by connecting the nodes on both banks, thus establishing a topographic-based river-estuary boundary. Above the bifurcation apex, the river is a single main channel without branches; below the bifurcation apex, the river formally splits into multiple distributaries.

[0026] S23: Determine the river-estuary boundary of the target area based on the tidal section interface; Specifically, the river-estuary boundary is determined based on the tidal zone interface, current interface, and saltwater intrusion interface of the tidal section of the river.

[0027] S24: Based on the river-estuary boundary based on salinity, the river-estuary boundary based on topography, and the river-estuary boundary based on the tidal section interface, obtain the degree of spatial overlap between any two river-estuary boundaries, so as to determine the overlapping area of ​​the buffer zone of the two river-estuary boundaries with the highest degree of overlap, and then determine the final river-estuary boundary of the target area.

[0028] Preferably, the formula used to obtain the degree of spatial overlap between any two river-estuary boundaries is as follows: (1) In the formula: The first The river-estuary boundary and the first The buffer zone area of ​​the river-estuary boundary (buffer zone width is 3 km); For the first The buffer zone of the river-estuary boundary and the first The area of ​​the overlapping buffer zone of the river-estuary boundary; For the first The river-estuary boundary and the first The degree of spatial overlap between the river-estuary boundaries, with a value range of 0 to 1, wherein when A value greater than 0.8 indicates a high degree of overlap between the boundaries; All are indexes of river-estuary boundaries.

[0029] Specifically, the river-estuary boundaries determined by various indicators will be spatially overlaid. Boundaries with high overlap (i.e., the two river-estuary boundaries with the highest degree of overlap) will be selected. Then, the overlapping area of ​​the buffer zone between these two river-estuary boundaries will be determined. Within this area, the water body zoning boundaries will be adjusted in conjunction with management boundaries (such as the outer edge of territorial waters, beautiful bay construction units, and priority protection units for ecological and environmental zoning) and areas where ecological and environmental problems occur (such as red tide-prone areas and low-oxygen core areas). This will determine the final river-estuary boundaries within the target area of ​​water body classification and zoning, ensuring that the boundaries conform to the synergistic characteristics of multiple indicators while accurately reflecting natural transition attributes. The specific adjustment method is as follows: when dividing ecological and environmental problem areas, beautiful bay construction units, etc., into two parts based on the determined boundaries, the water body zoning boundaries should be extended outward from the land towards the sea to ensure the integrity of ecological and environmental problem areas (such as red tide-prone areas and low-oxygen core areas), beautiful bay construction units, and priority protection units for ecological and environmental zoning.

[0030] Specifically, determining the boundaries on both sides of the estuary within the target area for water body classification and zoning includes: indicators for delineating the boundaries on both sides of the estuary include watershed distribution and administrative divisions, etc. The watershed distribution boundaries within the target area are used as the basis for delineation, combined with administrative division boundaries, to minimize the division of municipal administrative units.

[0031] Specifically, the method used to determine the estuary-coastal boundary within the target area for water body classification and zoning is as follows: the estuary-coastal boundary of the target area is determined based on the multi-year average isosalinity lines, wherein the salinity value used to determine the estuary-coastal boundary is greater than the salinity value used to determine the river-estuary boundary.

[0032] Specifically, the primary indicator for delineating the estuary-coastal boundary is salinity, using the same method employed to determine the river-estuary boundary based on salinity. Referring to the internationally accepted Venetian salinity classification system, a salinity of 30 is used as the boundary delineation criterion. A salinity of 30 is typically used as the boundary between high-salinity and true salinity zones. Compared to sea areas with salinity <30, sea areas with salinity ≥30 generally exhibit smaller salinity variations, resulting in relatively stable living conditions for marine life. This directly leads to significant differentiation in the biological community structure at different salinities: salinity <30 is dominated by low-salinity and euryhaline species, while salinity ≥30 is dominated by high-salinity species. Furthermore, as salinity increases above 30, the variety and abundance of biological species often show an increasing trend.

[0033] Specifically, after determining the river-estuary boundary, the boundaries on both sides of the estuary, and the estuary-nearshore boundary, a closed area will be formed based on these boundaries, namely the estuary area within the target area.

[0034] Specifically, a salinity of 0.5 is used as the boundary demarcation criterion: a salinity of 0.5 is generally used as the boundary between freshwater and saltwater (the initial river mouth boundary). S3: Based on the estuary unit zoning index, determine the estuary unit boundary within the estuary area to obtain several estuary unit zoning areas within the estuary area; the estuary unit zoning index is any one of salinity, water depth, and topography.

[0035] In this embodiment, the boundary of the estuary unit is determined within the estuary area. The main indicators used are salinity, water depth, and topography to divide the estuary area into zoning units.

[0036] When salinity is used to determine the boundaries of estuarine zoning units within an estuarine region, this embodiment refers to the internationally mainstream Venetian salinity classification system, using salinities of 6 and 18 as the basis for boundary delineation. A salinity of 18 is typically a differentiation node in the composition and spatial distribution of benthic communities, and also represents the optimal growth conditions for euryhaline species (within a salinity range of 10–25). Salinity ranges of 5–8 are critical or intermediate salinities, representing the ecological and physicochemical boundaries of transitional water bodies. Within this range, the abundance of both fresh and brackish water species is lowest, and the ratios of nutrients and ions exhibit clear transitional characteristics.

[0037] When using water depth to determine the boundaries of estuarine zoning units within an estuarine region, this embodiment uses the average annual water depth of the most recent year. Water depth can influence the habitat characteristics of estuarine / coastal ecosystems at multiple levels, such as stratification and mixing characteristics (thermocline depth) and light penetration, thereby affecting the distribution of biological communities. Therefore, water depth can be used as one of the effective indicators for water body zoning. 10 m, 30 m, and 50 m are used as the boundary delineation criteria: 10 m and 50 m water depths are generally considered typical distribution depths of the thermocline, while 30 m water depth is generally considered the upper limit of distribution depth for most seagrass species, possessing significant indicative significance for community habitats.

[0038] When using topography to determine the boundaries of estuarine zoning units within an estuarine region, lines connecting islands, low-tide elevations, and reefs that are close to the salinity and water depth boundaries are selected as the dividing boundaries of the estuarine zoning units.

[0039] S4: Obtain the test statistics within the estuary zoning unit to determine the probability value of the significance test within the estuary zoning unit, and then determine whether the selected estuary unit zoning indicators have ecological relevance. If the selected estuary unit zoning indicators are not ecologically relevant, then S3 is executed again based on the reselected estuary unit zoning indicators; until the selected estuary unit zoning indicators are ecologically relevant; the final estuary zoning units within the estuary area are determined, and the water body classification and zoning of the target area is completed.

[0040] Preferably, the method for obtaining the test statistic within the estuarine partition unit is as follows: When the number of estuarine zoning units is 2, an improved Mann-Whitney statistic calculation method is used to obtain the Mann-Whitney statistic for the estuarine zoning units in terms of biological and ecological indicators. The formula used is as follows: (2) (3) (4) In the formula, For the first The estuary partition unit is relative to the first Mann-Whitney statistics for each estuarine zoning unit on the k-th type of biological ecological indicator; For the first The estuary partition unit is relative to the first Mann-Whitney statistics for each estuarine zoning unit on the k-th type of biological ecological indicator; For the first Number of sampling points in each estuarine zoning unit (e.g., number of sampling points with salinity ≤ 18); For the first The number of sampling points in each estuary zoning unit; For the first The rank sum of the ratio of the number of the k-th type of biological and ecological indicators to the sum of the number of all biological and ecological indicators at all sampling points in a river estuary sub-unit after mixed sorting; For the first The rank sum of the ratio of the number of the k-th type of biological and ecological indicators to the sum of the number of all biological and ecological indicators at all sampling points in a river estuary sub-unit after mixed sorting; An index for biological and ecological indicators; This is the statistic used for significance testing; and All are index numbers of the estuary subdivision units; Specifically, U (k) U approximately follows a normal distribution (k) Standardized to z (k) Statistic:

[0041] In the formula: z (k) For standardized U (k) It approximately follows a standard normal distribution, if ≥1.96 α =0.05), then the probability value of the significance test is P <0.05. Among them,α The significance level; When the number of estuarine zoning units is greater than 2, an improved Kruskal-Wallis statistic calculation method is used to obtain the Kruskal-Wallis test statistics of the estuarine zoning units on biological and ecological indicators. The formula used is as follows: (5) (6) In the formula: The total number of sampling points for the k-th type of biological ecological indicator within the estuary area; This represents the total number of estuarine zoning units (e.g., divided into three groups based on salinity: 0.5~6, 6~18, and 18~30). For the first The number of sampling points in each estuary zoning unit; For the first The rank sum of the ratio of the number of the k-th type of biological and ecological indicators to the sum of the number of all biological and ecological indicators at all sampling points in a river estuary sub-unit after mixed sorting; This is the Kruskal-Wallis test statistic for the k-th type of biological ecological indicator.

[0042] Among them, H (k) It approximately follows a chi-square distribution with g-1 degrees of freedom, if H (k) ≥ Χ 2 (g-1,α) ( α =0.05), then the probability value of the significance test is P <0.05; X 2 The distribution follows a chi-square pattern, with α representing the significance level. In this embodiment, the probability value of the significance test for any biological ecological indicator exists. P When the value is less than 0.05, the selected estuarine unit zoning index is ecologically relevant.

[0043] Specifically, the significance of various biological and ecological indicators among the groups was analyzed according to the whole year and different seasons, and the probability of significance testing was used. P The value indicates that if a certain biological ecological indicator is... P <0.05 indicates a significant difference, suggesting that the selection of indicators for estuarine unit zoning has a certain ecological relevance; if all indicators... P If all values ​​are ≥0.05, it indicates that the differences are not significant, and the ecological relevance of the estuarine unit zoning indicators may be insufficient, so they should be reselected.

[0044] Preferably, the biological and ecological indicators include: nutrient use efficiency, phytoplankton cell density, number of phytoplankton species, proportion of phytoplankton group cell density to the total phytoplankton cell density, phytoplankton diversity index, phytoplankton richness index, and phytoplankton evenness index. Among them, nutrient salt utilization efficiency includes: chlorophyll a / total nitrogen, chlorophyll a / dissolved inorganic nitrogen, chlorophyll a / total phosphorus, and chlorophyll a / reactive phosphate. Phytoplankton include diatoms, dinoflagellates, cyanobacteria, green algae, golden algae, and yellow algae.

[0045] In this embodiment, the biological ecological indicators include: nutrient use efficiency, comprising: chlorophyll a / total nitrogen, chlorophyll a / dissolved inorganic nitrogen, chlorophyll a / total phosphorus, chlorophyll a / reactive phosphate, phytoplankton cell density and total density, where phytoplankton includes diatoms, dinoflagellates, cyanobacteria, green algae, golden algae, yellow algae, etc.; the number of phytoplankton species and total species, the proportion of phytoplankton groups (e.g., the proportion of diatom cell density to the total phytoplankton cell density), diversity index, richness index, and evenness index. The symbol " / " represents division by a factor.

[0046] Specifically, based on the zoning indicators (salinity, water depth, etc.) used to delineate estuarine zoning units, the proportions of phytoplankton communities (diatoms, dinoflagellates, cyanobacteria, green algae, golden algae, yellow algae, etc.) within the estuarine area are grouped according to the boundaries of the estuarine zoning units used. When the number of groups is two or more, the modified Mann-Whitney statistic or the Kruskal-Wallis statistic is used for significance testing to analyze the significant differences of each biological ecological indicator among the groups.

[0047] Preferably, after step S4, the method further includes: selecting evaluation indicators for estuarine zoning units and evaluating the estuarine zoning units; wherein the selected evaluation indicators for estuarine zoning units include biological and ecological indicators, water quality status indicators, and hydrological habitat indicators. The water quality indicators include total nitrogen, dissolved inorganic nitrogen, nitrate nitrogen, nitrite nitrogen, ammonia nitrogen, total phosphorus, reactive phosphate, dissolved oxygen at the bottom, transparency, and suspended solids. The hydrological habitat indicators include salinity, water depth, water temperature, stratified mixing characteristics, tidal range, salinity front, distribution of the maximum turbidity zone, sediment type, and water residence time.

[0048] Specifically, water quality indicators include nutrient indicators and other water quality indicators. Nutrient indicators include total nitrogen, dissolved inorganic nitrogen, nitrate nitrogen, nitrite nitrogen, ammonia nitrogen, total phosphorus, and reactive phosphate, while other water quality indicators include dissolved oxygen at the bottom, transparency, and suspended solids.

[0049] This embodiment obtains the estuarine zoning unit assessment indicators for evaluating the estuarine zoning units from the following sources: data obtained by ecological and environmental monitoring institutions and research institutes using standard methods, or publicly published literature or reports that have undergone peer review. The assessment indicators include biological and ecological indicators, water quality status indicators, and hydrological habitat indicators. Statistical methods are then used to assess the estuarine zoning units based on these indicators. ① For numerical indicators, analyze the significant differences of each indicator among different zonal units throughout the year and in different seasons to evaluate the estuarine zonal units. ② For descriptive indicators (stratified mixing characteristics, salinity front, distribution of maximum turbidity zone, sediment type, etc.), classify the indicators of each zonal unit according to the following characteristic types, or visually identify the spatial pattern differences between zonal units by drawing spatial distribution maps to achieve the evaluation of the estuarine zonal units.

[0050] a. Stratified blending characteristics: divided into permanent stratification, partial time stratification, and permanent blending.

[0051] Permanent stratification refers to the presence of a thermocline in seawater year-round; partial stratification refers to the presence of a thermocline with distinct seasonal variations; permanent mixing refers to seawater remaining almost homogeneous or nearly homogeneous year-round. If any of the temperature, salinity, or density parameters at a sampling point indicates the presence of a thermocline, it should be described as a stratified state. The stratification or mixing state of seawater is determined based on the thermocline strength. A strength below the minimum standard is generally considered mixed; otherwise, it is stratified. Generally, for water depths less than 200 m, the minimum standard for thermocline strength is as follows: Thermocline Strength Δ... T / Δ Z =0.2 ℃ / m, halocline strength Δ S / Δ Z =0.1 / m, dense layer Δ γ / Δ Z =0.1 kg / m 4 Δ Z For the depth difference, Δ T For temperature difference, Δ S For salinity difference, Δ γ This is due to density difference.

[0052] b. Salinity fronts: including shear fronts, estuary fronts, feathery fronts, cape fronts, etc.

[0053] c. Distribution of the maximum turbidity zone: present, absent.

[0054] d. Sediment types: including gravel (G), sandy gravel (sG), argillaceous sandy gravel (msG), argillaceous gravel (mG), gravelly sand (gS), gravelly argillaceous sand (gmS), gravelly mud (gM), gravelly sand ((g)S), gravelly argillaceous sand ((g)mS), gravelly mud ((g)M), sand (S), argillaceous sand (mS), sandy mud (sM), mud (M), sand (S), silty sand (zS), argillaceous sand (mS), clayey sand (cS), sandy silt (sZ), sandy mud (sM), sandy clay (sC), silt (Z), mud (M), clay (C), etc.

[0055] ③ Judgment criteria: When there are significant differences among the three categories of indicators—hydrological habitat, water quality, and biological ecology—among the different zoning units ( P <0.05) or different hydrological habitat types indicate that the zoning has a certain ecological relevance, and the results are reasonable; if there are no significant differences among all indicators between the two zoning units ( P If the descriptive indicators of hydrological habitat characteristics are all of the same characteristic type and are ≥0.05, they should be merged.

[0056] Example: Taking river mouths A and B as examples, the technical solution of the present invention will be further explained through specific embodiments.

[0057] 1. Determining the boundaries of water body classification zones: We used surface salinity data from national-level operational marine ecological environment monitoring over the past five years (data station locations are representative and can objectively reflect salinity distribution characteristics). We selected a continuous five-year series where runoff was roughly equal to the multi-year average to reduce interference from anomalous data under extreme weather conditions. Using the spatial analysis tools of ArcGIS software, we performed interpolation analysis using the inverse distance weighting method. Then, using the raster surface contour line function of the 3D analysis tool, we drew the multi-year average isosalinity lines for the region and extracted key salinity lines of 0.5, 6, 18, and 30 as the core basis for boundary delineation.

[0058] For the river-estuary boundary, in Estuary A (with a distinct braided structure), the 0.5 isosalinity line, the apex of the braids, and the saltwater intrusion interface of the tidal section are determined, and these three are spatially superimposed to define the river-estuary boundary. In Estuary B (without a distinct braided structure), the 0.5 isosalinity line and the tidal interface of the tidal section are determined, and the boundary is demarcated by connecting the administrative boundary nodes of the two shorelines. The specific boundary is adjusted according to the Beautiful Bay Construction Unit and the Priority Protection Unit for Ecological Environment Zoning Management, and the final river-estuary boundary is determined.

[0059] For the boundaries on both sides of the estuary, the specific boundaries are adjusted based on the watershed distribution boundaries and in conjunction with the Beautiful Bay Construction Unit and the priority protection unit for ecological environment zoning management, so as to avoid administrative unit division to the greatest extent and ensure the integrity of the watershed and the continuity of ecological protection units.

[0060] For the estuary-coastal boundary: the 30 isosalinity line is close to the outer edge of the territorial sea. At the same time, in order to ensure the integrity of the red tide-prone area and the low-oxygen core area, the boundary is appropriately adjusted to the east. The adjusted boundary ensures the integrity of the area where ecological and environmental problems occur.

[0061] For the boundaries of the estuary zoning units: based on the core delineation of the 18 isohaline, lines are drawn connecting islands and reefs close to the salinity boundaries. The specific boundaries are then adjusted in conjunction with the Beautiful Bay Construction Unit and the Priority Protection Unit for Ecological Environment Zoning Management. Two closed and clearly defined zoning units are delineated for both estuary A and estuary B, namely A1 and A2, and B1 and B2 from west to east. Figure 2 and Figure 3 As shown.

[0062] 2. Water body zoning unit assessment: (1) Zoning index assessment: The proportion of phytoplankton groups in the estuary was grouped according to a salinity of 18. The Kruskal-Wallis test results showed that salinity had a significant impact on the proportion of green algae, diatoms, and cyanobacteria in summer. P <0.05): When salinity <18, the proportions of the three groups are 3.0%, 80.4%, and 15.5%, respectively; when salinity ≥18, the proportions are 0.3%, 92.5%, and 0.3%, respectively. Figure 4 As shown, salinity as a zoning indicator has a clear ecological relevance.

[0063] (2) Zonal Unit Evaluation: The Kruskal-Wallis test results showed that water temperature, water depth, salinity, dissolved inorganic nitrogen, reactive phosphate, diatom species abundance, and algal utilization efficiency of nitrogen and phosphorus nutrients were generally significantly different among different zones, as shown in Table 1. In addition, each zone also showed certain differences in stratified mixing characteristics, tidal range, maximum turbidity zone, and sediment type, as shown in Table 2. In summary, the zonal units showed certain differences in hydrological, habitat, water quality, and biological ecology indicators, and the zoning results were relatively reasonable and had a certain degree of ecological relevance.

[0064] Table 1. Results of the significance test for estuarine water body zoning

[0065] Table 2. Hydrological and habitat assessment results of estuarine water body zoning units

[0066] Specifically, neither the "Marine Environmental Quality Assessment" (HJ 1300—2022) nor the "Seawater Quality Standard" (GB3097—1997) differentiates nutrient limits for different types of water bodies, such as estuaries and nearshore waters, making it difficult to meet the marine ecological environment protection and management needs of different regional characteristics. This embodiment takes the perspective of the river-estuary-nearshore continuum, using the Venice salinity classification system as the core, to determine the river-estuary boundary, the boundaries on both sides of the estuary, and the estuary-nearshore boundary to define the estuarine region; and further defines zoning units within the estuarine region. In this embodiment, the different estuarine zoning units within the estuarine region should reflect the differences in the sensitivity of phytoplankton to nutrient salt responses, generally ranging from 1 to 5. The estuarine zoning units are closed and clearly defined areas, and are simple and easy to operate, supporting relevant departments in carrying out marine ecological environment management work such as the establishment of estuarine-nearshore nutrient water quality benchmarks and estuarine water quality assessment. This embodiment comprehensively considers regional natural attributes and administrative planning, divides water bodies into ecologically relevant zoning units, improves the sensitivity differences of ecosystems to nutrient responses, and provides a key research basis for formulating nutrient water quality benchmarks for open estuaries in my country.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for classifying and zoning estuarine nutrient baseline water bodies based on differences in ecological response, characterized in that, Includes the following steps: S1: Obtain the multi-year average salinity of the surface layer of the target area for water body classification and zoning, the topography of the target area, and the tidal river interface of the target area. S2: Based on the multi-year average salinity of the surface water in the target area, the topography of the target area, and the tidal river section interface of the target area, the Venice salinity classification system is used to determine the river-estuary boundary, the two sides of the estuary boundary, and the estuary-nearshore boundary in the target area to be classified and zoned, so as to determine the estuary area in the target area. S3: Select any estuary unit zoning index to determine the boundary of the estuary zoning unit within the estuary area, so as to obtain several estuary zoning units within the estuary area. S4: Obtain the test statistics within the estuary zoning unit to determine the probability value of the significance test within the estuary zoning unit, and then determine whether the selected estuary unit zoning indicators have ecological relevance. If the selection of the estuary unit zoning indicators is not ecologically relevant, then S3 will be re-executed based on the re-selected estuary unit zoning indicators. Until the selected estuarine unit zoning indicators are ecologically relevant; Determine the final estuary zoning units within the estuary area to complete the water body classification and zoning of the target area.

2. The method for classifying and zoning estuarine nutrient baseline water bodies based on ecological response differences according to claim 1, characterized in that, The method used to determine the river-estuary boundaries within the target area for water body classification and zoning is as follows: S21: Obtain the multi-year average salinity of the surface layer of the water body within the target area to be classified and zoned, so as to obtain the multi-year average isosalinity line within the target area; and then determine the salinity-based river-estuary boundary of the target area based on the multi-year average isosalinity line. S22: Determine the topographic-based river-estuary boundary of the target area; S23: Determine the river-estuary boundary of the target area based on the tidal section interface; S24: Based on the river-estuary boundary based on salinity, the river-estuary boundary based on topography, and the river-estuary boundary based on the tidal section interface, obtain the degree of spatial overlap between any two river-estuary boundaries, so as to determine the overlapping area of ​​the buffer zone of the two river-estuary boundaries with the highest degree of overlap, and then determine the final river-estuary boundary of the target area.

3. The method for classifying and zoning estuarine nutrient baseline water bodies based on ecological response differences according to claim 2, characterized in that, The formula used to obtain the degree of spatial overlap between any two river-estuary boundaries is as follows: （1） In the formula: The first The river-estuary boundary and the first The buffer zone area of ​​the river-estuary boundary; For the first The buffer zone of the river-estuary boundary and the first The area of ​​the overlapping buffer zone of the river-estuary boundary; For the first The river-estuary boundary and the first The degree of spatial overlap between the river-estuary boundaries; All are indexes of river-estuary boundaries.

4. The method for classifying and zoning estuarine nutrient baseline water bodies based on ecological response differences according to claim 1, characterized in that, The method for obtaining the test statistic within the estuarine partition unit is as follows: When the number of estuarine zoning units is 2, an improved Mann-Whitney statistic calculation method is used to obtain the Mann-Whitney statistic for the estuarine zoning units in terms of biological and ecological indicators. The formula used is as follows: （2） （3） （4） In the formula, For the first The estuary partition unit is relative to the first Mann-Whitney statistics for each estuarine zoning unit on the k-th type of biological ecological indicator; For the first The estuary partition unit is relative to the first Mann-Whitney statistics for each estuarine zoning unit on the k-th type of biological ecological indicator; For the first The number of sampling points in each estuary zoning unit; For the first The number of sampling points in each estuary zoning unit; For the first The rank sum of the ratio of the number of the k-th type of biological and ecological indicators to the sum of the number of all biological and ecological indicators at all sampling points in a river estuary sub-unit after mixed sorting; For the first The rank sum of the ratio of the number of the k-th type of biological and ecological indicators to the sum of the number of all biological and ecological indicators at all sampling points in a river estuary sub-unit after mixed sorting; An index for biological and ecological indicators; This is the statistic used for significance testing; and All are index numbers of the estuary subdivision units; When the number of estuarine zoning units is greater than 2, an improved Kruskal-Wallis statistic calculation method is used to obtain the Kruskal-Wallis test statistics of the estuarine zoning units on biological and ecological indicators. The formula used is as follows: （5） （6） In the formula: The total number of sampling points for the k-th type of biological ecological indicator within the estuary area; This represents the total number of estuarine subdivision units; For the first The number of sampling points in each estuary zoning unit; For the first The rank sum of the ratio of the number of the k-th type of biological and ecological indicators to the sum of the number of all biological and ecological indicators at all sampling points in a river estuary sub-unit after mixed sorting; This is the Kruskal-Wallis test statistic for the k-th type of biological ecological indicator.

5. The method for classifying and zoning estuarine nutrient baseline water bodies based on ecological response differences according to claim 4, characterized in that, The biological and ecological indicators include: nutrient use efficiency, phytoplankton cell density, number of phytoplankton species, proportion of phytoplankton group cell density to total phytoplankton cell density, phytoplankton diversity index, phytoplankton richness index, and phytoplankton evenness index. Among them, nutrient salt utilization efficiency includes: chlorophyll a / total nitrogen, chlorophyll a / dissolved inorganic nitrogen, chlorophyll a / total phosphorus, and chlorophyll a / reactive phosphate. Phytoplankton include diatoms, dinoflagellates, cyanobacteria, green algae, golden algae, and yellow algae.

6. The method for classifying and zoning estuarine nutrient baseline water bodies based on ecological response differences according to claim 1, characterized in that, The S4 section further includes: selecting estuarine zoning unit evaluation indicators and evaluating the estuarine zoning unit; wherein the selected estuarine zoning unit evaluation indicators include biological and ecological indicators, water quality status indicators, and hydrological habitat indicators. The water quality indicators include total nitrogen, dissolved inorganic nitrogen, nitrate nitrogen, nitrite nitrogen, ammonia nitrogen, total phosphorus, reactive phosphate, dissolved oxygen at the bottom, transparency, and suspended solids; The hydrological habitat indicators include salinity, water depth, water temperature, stratified mixing characteristics, tidal range, salinity front, distribution of the maximum turbidity zone, sediment type, and water residence time.

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